Ostara is the Spring equinox. Equinoxes are a time of balance. This would be the waxing equinox in which the sun would continue to grow in the sky. Celebrate the fertility of the land, first flowers of springs. Green/yellow are important colors, Green being vegetative representing earth and yellow being sun representing balance. The egg is symbolic of balance as well as fertility/rebirth. The yolk is representative of new birth/sun/god with the white shell is the goddess protecting that which grows in her womb. In some native american cultures this would be the time of saying goodbye to Waboose, the Winter (North) represented by the white buffalo and containing the powers of cleansing renewal and purification. In turn they would welcome Wabun, the Spring (East) represented by the eagle and containing the powers of clarity, wisdom and illumination.